1. Field of the Invention
The present invention is generally related to a wireless network of a tree topology. More particularly, the present invention is directed to a method for optimally recovering a broken route, while maintaining an existing tree route, in case of a failure of a node or a link configuring a wireless tree network.
2. Description of the Related Art
Recent developments of Internet and mobile communication technologies provide diverse multimedia services, which may be presented almost instantaneously even over vast distances, so as to remarkably change its users' lives. Particularly, with the prevalence of compact portable electronic devices such as notebook computers and personal digital assistants (PDA), more efforts are made to implement data communications through not only wired networks but also wireless networks.
A representative wireless network is an ad-hoc network. The ad-hoc network has no central and integral management device, does not utilize an existing communication infrastructure, and has no control device, such as a router, a host, or a mobile base station, for providing links between mobile nodes. Instead, the mobile nodes act as routers. Accordingly, when a certain mobile node intends to communicate with a correspondent node, the mobile node needs to establish a communication path to the correspondent node via other nodes located between the mobile node and the correspondent node.
An example of an ad-hoc network is a wireless network having a tree structure. The tree structure is widely used in ad-hoc networks because the tree structure has good addressing and routing features. The tree-structured network sequentially assigns addresses according to a tree hierarchy and packets are delivered along a tree route.
However, if a node configuring the network of the tree structure fails due to a battery discharge or failure, movement out of the network, or a link is disconnected, any descendent nodes of a broken node or link have to re-establish and recover a communication route in thee tree structure.
A conventional algorithm re-establishes a route in a manner that each descendent node of a broken node or link attempts to re-connect to the network. The conventional algorithm results in a control overload problem, address changes of the existing tree structure, and changes of the topology of the existing tree structure.
Additionally, the descendent nodes of the broken link have to update an information table which contains information such as a local address, a depth in the tree structure, and a list of neighbor nodes. If the broken link is related to a node of an upper layer, a lower tree structure is adversely affected and a new link needs to be configured.